Just maintain hobbies that you regularly go to and that bring you around other people, push through your comfort zone and maintain your health so that your brain is functioning optimally and you have a positive outlook and want to socialize. That means avoiding drug abuse of any kind, p0rn/masturbation and eating a nutrient dense and non-inflammatory diet most of the time (low-carb/carnivore leaning).
As for the hobbies, volunteer at animal shelters where loads of other people go, join sporting clubs, maybe a crossfit gym, a weekly basketball game, a book club where people meet often to discuss the books being read, a writing club, regularly volunteering at your local masjid or generally anything you like and think you'd benefit from where you'd be around other people for at least a few hours on a weekly or more than once a week basis if you can crack it with your work schedule. If you're feeling good and push through that initial awkwardness, you'll make as many friends as when you were in college if not more.
Finally, most cities have online groups on Facebook, Discord and Meetup where they regularly arrange meetup events like boardgame nights, clubbing nights, dinners, tours of certain museums or whatever else. Go. You'd be surprised how quickly you can make friends via these sorts of events and most of these groups are meant for people who are college grads or new to a city with names like "Friends after college" or what have you.
Best of luck, cuz.